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Subject: [PATCH v6 02/11] device-dax/kmem: introduce dax_kmem_range()
From:   Dan Williams <dan.j.williams@intel.com>
To:     akpm@linux-foundation.org
Cc:     David Hildenbrand <david@redhat.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Brice Goglin <Brice.Goglin@inria.fr>,
        Dave Jiang <dave.jiang@intel.com>,
        Ira Weiny <ira.weiny@intel.com>, Jia He <justin.he@arm.com>,
        Joao Martins <joao.m.martins@oracle.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        David Hildenbrand <david@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org,
        david@redhat.com, joao.m.martins@oracle.com
Date:   Mon, 05 Oct 2020 23:54:56 -0700
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In-Reply-To: <160196728453.2166475.12832711415715687418.stgit@dwillia2-desk3.amr.corp.intel.com>
References: <160196728453.2166475.12832711415715687418.stgit@dwillia2-desk3.amr.corp.intel.com>
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Towards removing the mode specific @dax_kmem_res attribute from the
generic 'struct dev_dax', and preparing for multi-range support, teach
the driver to calculate the hotplug range from the device range. The
hotplug range is the trivially calculated memory-block-size aligned
version of the device range.

Cc: David Hildenbrand <david@redhat.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jia He <justin.he@arm.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/dax/kmem.c |   40 +++++++++++++++++-----------------------
 1 file changed, 17 insertions(+), 23 deletions(-)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 5bb133df147d..b0d6a99cf12d 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -19,13 +19,20 @@ static const char *kmem_name;
 /* Set if any memory will remain added when the driver will be unloaded. */
 static bool any_hotremove_failed;
 
+static struct range dax_kmem_range(struct dev_dax *dev_dax)
+{
+	struct range range;
+
+	/* memory-block align the hotplug range */
+	range.start = ALIGN(dev_dax->range.start, memory_block_size_bytes());
+	range.end = ALIGN_DOWN(dev_dax->range.end + 1, memory_block_size_bytes()) - 1;
+	return range;
+}
+
 int dev_dax_kmem_probe(struct device *dev)
 {
 	struct dev_dax *dev_dax = to_dev_dax(dev);
-	struct range *range = &dev_dax->range;
-	resource_size_t kmem_start;
-	resource_size_t kmem_size;
-	resource_size_t kmem_end;
+	struct range range = dax_kmem_range(dev_dax);
 	struct resource *new_res;
 	const char *new_res_name;
 	int numa_node;
@@ -44,25 +51,14 @@ int dev_dax_kmem_probe(struct device *dev)
 		return -EINVAL;
 	}
 
-	/* Hotplug starting at the beginning of the next block: */
-	kmem_start = ALIGN(range->start, memory_block_size_bytes());
-
-	kmem_size = range_len(range);
-	/* Adjust the size down to compensate for moving up kmem_start: */
-	kmem_size -= kmem_start - range->start;
-	/* Align the size down to cover only complete blocks: */
-	kmem_size &= ~(memory_block_size_bytes() - 1);
-	kmem_end = kmem_start + kmem_size;
-
 	new_res_name = kstrdup(dev_name(dev), GFP_KERNEL);
 	if (!new_res_name)
 		return -ENOMEM;
 
 	/* Region is permanently reserved if hotremove fails. */
-	new_res = request_mem_region(kmem_start, kmem_size, new_res_name);
+	new_res = request_mem_region(range.start, range_len(&range), new_res_name);
 	if (!new_res) {
-		dev_warn(dev, "could not reserve region [%pa-%pa]\n",
-			 &kmem_start, &kmem_end);
+		dev_warn(dev, "could not reserve region [%#llx-%#llx]\n", range.start, range.end);
 		kfree(new_res_name);
 		return -EBUSY;
 	}
@@ -96,9 +92,8 @@ int dev_dax_kmem_probe(struct device *dev)
 static int dev_dax_kmem_remove(struct device *dev)
 {
 	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct range range = dax_kmem_range(dev_dax);
 	struct resource *res = dev_dax->dax_kmem_res;
-	resource_size_t kmem_start = res->start;
-	resource_size_t kmem_size = resource_size(res);
 	const char *res_name = res->name;
 	int rc;
 
@@ -108,12 +103,11 @@ static int dev_dax_kmem_remove(struct device *dev)
 	 * there is no way to hotremove this memory until reboot because device
 	 * unbind will succeed even if we return failure.
 	 */
-	rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size);
+	rc = remove_memory(dev_dax->target_node, range.start, range_len(&range));
 	if (rc) {
 		any_hotremove_failed = true;
-		dev_err(dev,
-			"DAX region %pR cannot be hotremoved until the next reboot\n",
-			res);
+		dev_err(dev, "%#llx-%#llx cannot be hotremoved until the next reboot\n",
+				range.start, range.end);
 		return rc;
 	}